U.S. Pat. Nos. 4,006,049 and 4,058,428 are directed to pipe coating apparatus. This disclosure is an improvement in the structure of the reference pipe coating apparatus. As a practical matter, concrete which is applied to a pipe as weight material normally requires reinforcing mesh to enhance its strength. As a generalization, concrete is very weak in tension. In the handling of pipe with a concrete coating thereon, inevitably, certain parts of the coating material are loaded in tension. When tension is applied, the concrete will crack and break away from the pipe.
The reference patents disclose pipe coating apparatus with a single wrap. This disclosure is directed to a multiple wrap of reinforcing mesh. Multiple layers of reinforcing mesh wire provide enhanced strength and are able to prevent breaking or cracking of thicker layers of weight material. As an example, the referenced patents do quite well in placing weight material on a pipe up to a fairly significant thickness. Dependent on the thickness required, the handling to be encountered after curing, the size, length and flexure of the pipe and a number of other factors, it is sometimes desirable to incorporate an additional layer of reinforcing mesh wire in the coating material to prevent breaking.
This disclosure describes a pipe coating apparatus having a feature enabling multiple wraps of reinforcing mesh to be placed in the weight material.
It is not quite so easy to simply add layers of reinforcing mesh wire. As layers are added, a problem arises in that adjacent turns of the coating material applied in helical fashion around the pipe are crushed against prior turns. This folds the reinforcing mesh in an odd manner at the edges. So to speak, adjacent turns of the same strip of reinforcing wire mesh provide greater strength if they lap over and are almost contacted against one another. As adjacent turns are crushed into the prior turns of coating material, the lip or margin of the previous turn is crushed down, thereby preventing a single strip from defining an encircling cylinder of structural reinforcing wire mesh within the concrete.
This apparatus overcomes that difficulty. This apparatus places adjacent turns of the reinforcing mesh in the concrete in the general form of a cylinder so that strength is increased, and the holding ability is enhanced. If, for instance, two or more layers of reinforcing wire mesh are placed in the coating material, they are lapped over at their edges to define two or more generally concentric cylinders of structural reinforcement within the thicker coat of concrete material. This is achieved in part by an alternate form of shaping the ribbon of concrete material which is carried on the conveyor system toward the pipe.
With the foregoing features and advantages in mind, this apparatus is an improved pipe coating apparatus featuring an upstanding funnel-shaped hopper or bin which receives a continuous supply of coating material. It is positioned above a conveyor belt. One feature of this invention is the incorporation of multiple slots in the back side of the hopper. This enables multiple strips of reinforcing wire mesh to be fed into the extruded ribbon of coating material. They are positioned at relative heights above the conveyor belt and are offset from one another. Moreover, they pass through the hopper and emerge with a ribbon of coating material. The ribbon of coating material is shaped into steps so that the top face thereof is stepped from edge to edge. The position of the steps is related to the relative position of the strips of reinforcing wire mesh. The ribbon of coating material is crushed against the pipe in conjunction with the roller beneath the pipe which guides the conveyor belt, and the steps are matched against the coating material applied in the previous turn, thereby enabling the pipe to be coated to a much greater thickness with reinforcing mesh.